Zombie Coins Drop x9999

Hello guys, I've been played the Defense against the zombies, when I killed some mobs, I got a drop (White box), when the round finished I saw "You got x9999 coins", after finishing my game, It does not let me craft any weapon, when I refresh the game, the coins reduces back at 2 coins, seems like they take off my drop... or I don't know if you can get a lot of coins by lucky in a drop, can someone answer me, or the admins of Crossfire can return the drop I got ?